Attempts have been made to covalently link certain drugs, for example, taxol, cisplatin, methotrexate, and ibuprofen, to dendrimers, which are polymers made from branched monomers through the iterative organic synthesis by adding one layer (i.e., generation) at each step to provide a symmetrical structure. Such dendrimer conjugates have one or more advantages, for example, altered pharmacokinetics, decreased toxicity, and increased solubility. Agonists and antagonists of the receptors of the G-protein coupled receptor (GPCR) superfamily are useful in the treatment of a number of diseases, for example, the agonist of one member of the GPCR superfamily, the A1 adenosine receptor, is useful for treating a number of diseases including cognitive disease, stroke, epilepsy, and migraine. There is a desire to obtain dendrimer conjugates of agonists and antagonists of the GPCR superfamily of receptors.